Technical Field
The invention relates to the art of disc brakes for heavy-duty vehicles. More particularly, the invention relates to rotors of disc brakes for heavy-duty vehicles. Still more particularly, the invention is directed to a shield that protects a rotor of a disc brake. The shield includes a smooth radially-extending wall and a smooth axially-angled wall, which provide direct protection against road spray and reduce the buildup of contaminants, thereby reducing corrosion of the rotor and optimizing the performance and life of the rotor and corresponding brake pads.
Background Art
Disc brake systems for vehicles are well known in the brake art. Such systems operate by forcing a pair of opposing brake pads against a rotor, thereby creating friction between the pads and the rotor to enable slowing and/or stopping of the vehicle. More particularly, a disc brake system includes a plurality of disc brake assemblies, in which each assembly is operatively mounted on or adjacent a wheel end of the vehicle.
Each disc brake assembly includes a carrier, which supports a caliper that is described in greater detail below, and is attached to a torque plate, typically by mechanical fasteners, such as bolts. The torque plate in turn is rigidly connected to an axle of an axle/suspension system of the vehicle, such as by welding. The torque plate resists the torque that is generated during braking, and maintains proper alignment of the carrier and caliper to ensure optimum operation of the components of the brake assembly.
As mentioned above, the carrier supports a caliper, and the caliper is formed with a bore for receiving one or more pistons and an actuator. The actuator typically is a brake air chamber, which is in fluid communication with a compressed air source and activates movement of the piston(s). The caliper also includes an outboard pad seat that is disposed opposite the piston(s). Each one of a pair of opposing brake pads includes friction material that is mounted on a backing plate, and is seated in the carrier, with one of the pads being adjacent the piston(s) and the other pad being adjacent the outboard pad seat. Upon actuation by the actuator, the piston(s) and the outboard pad seat cooperate to control movement of the brake pads.
The rotor includes a disc portion, which is disposed between the brake pads in a manner that allows the friction material of each pad to face a respective one of a pair of surfaces of the disc portion. The rotor also includes a mounting portion that is adapted for mounting to a respective one of the wheel end assemblies of the vehicle by mechanical fasteners, such as bolts. A sleeve typically is integrally formed with and extends between the disc portion and the mounting portion of the rotor. This construction enables the rotor to be rigidly connected to the wheel end assembly, and thus to its respective vehicle wheel.
During vehicle travel, when the vehicle brake system is engaged, compressed air flows to the actuator, which engages movement of the piston(s) and the outboard pad seat, which in turn forces the friction material of the pads against the disc portion of the rotor, slowing and/or stopping rotation of the rotor, thereby slowing and/or stopping rotation of the vehicle wheel. It is known in the art that, during normal operation of a heavy-duty vehicle, certain contaminants and road conditions can cause the rotor to corrode, which reduces the performance and life of the brake rotor and the brake pads.
More particularly, when a heavy-duty vehicle travels over roads, abrasive contaminants such as dirt, sand, mud, snow, and the like contact the underside of the vehicle. For the purpose of convenience, such abrasive contaminants shall collectively be referred to as contaminants. Because the brake assemblies are located on the lower portion of the vehicle, contaminants tend to collect on certain components of the disc brake assembly, including the rotor and surfaces proximate the rotor. When contaminants collect and build up on the rotor and such surfaces, they may create a scouring effect on the rotor, which makes the rotor more susceptible to corrosion.
In addition, when a heavy-duty vehicle travels over roads and there is moisture on the road surface, road spray may be generated. Road spray is the moisture that is caused to move upward from the road surface by the vehicle tires toward the underside of the vehicle. In addition, cross splash may be generated, which is the splashing of moisture from puddles toward the underside of the vehicle when a vehicle tire contacts a puddle. By contacting the underside of the vehicle, road spray and cross splash contact many exposed components on the lower portion of the vehicle. Because the brake assemblies are located on the lower portion of the vehicle, when the vehicle travels over wet roads, road spray and cross splash tend to collect on certain components of the disc brake assembly, including the rotor. For the purpose of convenience, reference below shall be made to road spray with the understanding that such reference includes both road spray and cross splash.
It is known in the art that road spray may include salt or other chemicals that are present on the road surface. For example, salt from salt water is often present on roads near a sea, and roads in areas with abundant ice or snow are often treated with certain chemicals for anti-icing or de-icing. Anti-icing and de-icing shall collectively be referred to herein for the purpose of convenience as anti-icing. Such anti-icing chemicals include sodium chloride, calcium chloride, magnesium chloride, and mixtures thereof. In the past, sodium chloride, which is commonly referred to as road salt, had typically been used to treat roads for anti-icing. However, more aggressive anti-icing chemicals have been developed, including calcium chloride and magnesium chloride. Because road spray includes such salt or other chemicals, the road spray that collects on the rotor thus includes the salt and/or other chemicals. The collection of road spray that includes salt and/or anti-icing chemicals, and in particular the more aggressive anti-icing chemicals, can cause corrosion of the rotor. Such corrosion may be exacerbated by the above-described scouring effect of the rotor by contaminants. It is to be understood that reference herein to road spray includes the above-described anti-icing chemicals.
The inboard surface of the rotor disc, which shall be referred to herein for the purpose of convenience as the inboard surface of the rotor, is particularly exposed to road spray and contaminants, and thus is more susceptible to corrosion. When the inboard surface of the rotor corrodes, the corresponding brake pad wears prematurely from contact with the corroded surface, which reduces the performance and life of the rotor and at least the inboard brake pad. To reduce the amount of road spray and contaminants that contact the inboard surface of the rotor, shields have been employed in the prior art. Such shields typically are rigidly attached to the axle or the torque plate inboardly of the rotor, and thus are statically-mounted structures that attempt to prevent direct contact of road spray and contaminants with the inboard surface of the rotor.
One exemplary prior art shield includes a simple radially-extending wall that is bolted to the inboard surface of the torque plate. Rotor shields of this particular design extend radially from the outer surface of the axle to slightly past the outer periphery or edge of the rotor. Because the attachment location at the inboard surface of the torque plate is spaced about an inch or more from the rotor, and the shield is a single flat wall, road spray and contaminants may easily work around the shield and contact the inboard surface of the rotor. Therefore rotor shields of this design provide very limited protection from road spray and contaminants.
In other types of prior art rotor shields, the shield includes a radially-extending wall portion that is bolted to projections formed on the torque plate, and which typically are cast as part of the torque plate. The radially-extending wall portion of a rotor shield of this design typically extends radially past the outer periphery or edge of the rotor. The shield then bends at about a ninety-degree angle to form an axially-extending wall portion that extends outboardly over a portion of the outer periphery of the rotor disc. The radially-extending wall portion is formed with a plurality of spaced-apart features, including vent louvres and indentations, which are intended to allow road spray and contaminants to escape from the space between the inboard surface of the rotor and the shield. However, over time, the features often trap and hold contaminants, which in turn undesirably increases the exposure of the inboard surface of the rotor to road spray and contaminants.
Still other types of prior art shields include a radially-extending wall portion that is clamped or otherwise rigidly attached to the axle adjacent the outboard surface of the torque plate, and which extends radially past the outer edge or periphery of the rotor. The shield then bends at about a ninety-degree angle to form an axially-extending wall portion or lip that extends outboardly over a portion of the outer periphery of the rotor disc. However, due to the attachment of the shield adjacent the outboard surface of the torque plate, the shield is in extremely close proximity to the inboard surface and the outer periphery of the rotor. Such a close proximity, combined with an axially-extending wall, inhibits the escape of road spray and contaminants that pass by the shield, which in turn undesirably increases the exposure of the inboard surface of the rotor to road spray and contaminants.
As a result, there is a need in the art for a protection shield for a rotor of a disc brake for heavy-duty vehicles that provides direct protection against road spray and reduces the buildup of contaminants, thereby reducing corrosion of the inboard surface of the rotor and optimizing the performance and life of the rotor and corresponding brake pad(s). The rotor protection shield for heavy-duty vehicles of the present invention satisfies these needs, as will be described in detail below.